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Hello fellow maintenance engineer,

I would like to share about high vibration problem in multistage high pressure pump, and hopefully you guys might help in resolving this problem

This pump is turbine driven boiler feed pump, with 2 plain bearings on drive end side, and 1 thrust bearing on non drive end side to handle high axial load. The pump is directly coupled and the turbine speed is varied throughout operation according to operation load.

We recently replaced all pump bearings and mechanical seals upon customer's request due to high vibration for the past year. But the high vibration still occur after those minor overhaul

There is high peak on vertical side at 0.77X and 1X. While on horizontal side shown 0.5X, 0.77X, 1X and also BPF peak. Attached the spectral data

My first thought is the pump might have worn clearance in wearing, but when I plot the operating data to pump curve the pump is still operating within the curve. Since then, I suspect balance drum might be over-clearance and this causes rotor instability because I haven't check the clearance of balance drum. And also I suspect there might be resonance on rotor, but my concern is this pump already operating on its designed speed at 5345 rpm and have been operating for about 8 years. Do critical speed could change in time?

I would appreciate if you have any suggestion for resolving this problem


Tags: Subsynchronous, BPF

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@Registered Member posted:

@Registered Member

Ralph, thank you for replying

Attached the sectional drawing for this pump, 603.13 is the balance drum, while 602.02 is the counterbalanc


Thanks for the reply, but I can not find (or see) your original posting and the "replies" from others before my first reply . Have you or someone deleted it?

I do not see anything except your reply to my first reply, and the opening greeting to, "Hello fellow maintenance engineer,"  nor do I see my first reply with a picture and questions.

Strange....................... Any ideas why I can not see them?




I am totally confused as to what is wrong with this thread and the replies and why I can not see all the the replies,or my last image I posted.

I am posting the image again. Seems as though, somehow, I have been partially block out of the thread or there may be something wrong with my computer.????????????????????????

Thanks for any help on why this might be happening.

If I am "blocked-out", tell me and I will cease to question this problem.

Here is the image I posted earlier.


Sidebands on 1x rpm question 06-22-2022


Images (1)
  • Sidebands on 1x rpm question 06-22-2022

@Registered Member Hey Ralph, thanks again for replying. I attached the wrong files, my bad. Attached the sectional drawing. For the trouble in viewing images have you try to re-login?

For the spectrum, as I could tell there is no sidebands, at first I thought I saw sidebands too, but turns out it is subsynchronous peak at 69 Hz, pump 1X is at 88.9 Hz. For change in operation, as you can see in my other attachment files, there is change in flow and pressure but it was affected by the speed and I think the best efficiency point is not moving much. Also highest value vibration was at its design speed (88.9 Hz)

I haven't been able to go to site to view it myself, I only analyzed data that was provided to me, but I got information that the vibration is at its highest is when operating at full load (design speed operation)



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